Decentralized practical tracking by output-feedback for uncertain nonlinear systems with unknown growth rate

This paper considers decentralized adaptive practical tracking via output feedback for nonlinear systems with only the tracking error measurable. Substantially different from the related works, not only the nonlinearities but also the interaction terms, have unmeasured states dependent linear growth with unknown constant rate, and the reference signal, as well as its derivative, has bounds but unknown. This makes the problem difficult to solve. In the paper, motivated by the related tracking result [10], and flexibly using the ideas and techniques of universal control and dead zone, a decentralized adaptive output-feedback controller is explicitly designed. It is shown that all the signals in the closed-loop system obtained are bounded, and global practical tracking is achieved.